title: Usefulness of the combined IgG and IgA antibody determinations for serodiagnosis of Helicobacter pylori infection.
abstract: BACKGROUND
  Serology is a good alternative, minimally invasive, diagnostic and screening test for Helicobacter pylori infection. Several immunoglobulin G (IgG) enzyme-linked immunosorbent assay (ELISA) commercial kits have been evaluated. Information on IgA ELISAs is relatively poor, and on the combined use of IgG and IgA ELISAs very scarce.
  
  
  OBJECTIVE
  We intended to evaluate the sensitivity, specificity and predictive values of two quantitative commercial IgG and IgA ELISAs (Helico-G and GAP, respectively) and more particularly the accuracy of their combined use.
  
  
  METHODS
  Serum samples and gastric biopsy specimen culture findings from 400 patients were evaluated.
  
  
  RESULTS
  The sensitivity, specificity, positive and negative predictive values of the IgG ELISA Helico-G test in detecting IgG antibodies to H. pylori were 97.2, 85.4, 98.3 and 77.8%, respectively, when compared with those of the reference method used. The corresponding findings for detection of IgA antibodies with the GAP test were 96.4, 80.5, 97.7 and 71.1%, respectively. When considering a patient infected with H. pylori when both tests were positive, the sensitivity, specificity, positive and negative predictive values were 94.1, 85.3, 98.2 and 62.5%, respectively. On the other hand, when at least one test was positive, the corresponding values were 99, 80, 97 and 94%, respectively.
  
  
  CONCLUSIONS
  The IgG ELISA Helico-G and IgA ELISA GAP, taken separately, are good and reliable tests for the detection of antibodies to H. pylori. Furthermore, the combined use of both serological methods provided more useful information compared with single IgG and IgA determinations.
authors.affiliation: Department of Gastroenterology, University of Alcalá de Henares, Ramón y Cajal Hospital, Madrid, Spain.
authors.forename: C
authors.initials: C
authors.lastname: Martín-de-Argila
authors.forename: D
authors.initials: D
authors.lastname: Boixeda
authors.forename: R
authors.initials: R
authors.lastname: Cantón
authors.forename: S
authors.initials: S
authors.lastname: Valdezate
authors.forename: N
authors.initials: N
authors.lastname: Mir
authors.forename: L
authors.initials: L
authors.lastname: De Rafael
authors.forename: J P
authors.initials: JP
authors.lastname: Gisbert
authors.forename: F
authors.initials: F
authors.lastname: Baquero
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D004797:Enzyme-Linked Immunosorbent Assay / Q000379:methods*; D005260:Female; D005767:Gastrointestinal Diseases / Q000150:complications / Q000175:diagnosis; D016481:Helicobacter Infections / Q000150:complications / Q000175:diagnosis*; D016480:Helicobacter pylori; D006801:Humans; D007070:Immunoglobulin A / Q000097:blood*; D007074:Immunoglobulin G / Q000097:blood*; D008297:Male; D008875:Middle Aged; D011237:Predictive Value of Tests; D012680:Sensitivity and Specificity; D012698:Serologic Tests
chemical_list: D007070:Immunoglobulin A; D007074:Immunoglobulin G